Peripheral sensory neurons of the visual and somatosensory systems can be divided into different types based on molecular, morphological, and functional characteristics. These various neuron types contribute to parallel pathways that code different aspects of sensation. The taste receptor cells which transduce the chemicals in the food we eat exist as types. It is unclear whether there are types of geniculate ganglion neurons, which carry this information from taste buds to the brainstem. Differential expression of the neurotrophin receptor, TrkB, in half of the taste neurons could be an indicator that these neurons do exist as different types. If this is the case, TrkB-expressing taste neurons should be developmentally, functionally and morphologically distinctive from neurons that lack TrkB. The goal of this study is to examine this possibility using genetic labeling, electrophysiology, conditional knockout mice, taste nerve labeling and tract tracing. I will use these approaches to determine 1) if adult TrkB expressing neurons arise differently during development than TrkB-negative taste neurons; 2) if adult TrkB-expressing neurons have a specific function; 3) if adult TrkB-neurons have specific projections to the NTS. Together these experiments will test the hypothesis that that TrkB expression divides gustatory neurons in half, and that these two groups of taste neurons differ in their development, function, and CNS projections. If my proposed hypothesis is correct, this would provide the first evidence that gustatory neurons can be divided into types based on intrinsic criteria. Understanding how the taste system develops and is organized in adulthood is imperative for taste system repair following disruption. For example, both middle ear surgeries and basal cell carcinoma treatment disrupt gustatory structure and function. This study could contribute to the design of improved treatment that will offer better quality of life to patients with taste disturbances.